Papers by Keyword: Heat Conduction

Abstract: Jominy end quench test is a standardized metallurgical experiment for obtaining data on steel hardenability. Construction of numerical simulation of the test provides a way for parameterizing and validation of numerical models using the experimental data. In the current work we present the coupled heat transfer, conduction and phase transformation model, which allows for calculation of phase fractions at different positions at the Jominy test piece, and includes the latent heat released by the phase transformations. Also, the temperature and phase fraction dependence of the thermal conductivity is included in the calculation.

Abstract: The work discusses the problem of development of a heat-protective coating for objects of various purposes which are subjected to the external high-temperature impact. As a solution of the problem the application of heat-absorbing components providing the thermal barrier effect conducing to refraction of heat flows directed to heating of the protected object in the recipe of a heat-protective coating is presented. Temperature conditions of the protected object are provided due to the endothermic reaction which passes in the heat-protective layer by reaching the temperature of the selected component decomposition. Besides, the temperature of the heat absorption reaction has to be lower than the lesion temperature of the protected object.

Abstract: Carbon fiber reinforced carbon composites (C/C composites) have been important structural materials at high temperatures. C/C composites are anisotropic solids and their thermal diffusivity is the second-order tensor of which components are called thermal diffusivity coefficients. Therefore, the purpose of study is to measure the thermal diffusivity in direction parallel to fiber and that in direction perpendicular to fiber by using the step heating method. This report demonstrates the correctness of the method to determine the thermal diffusivity in principal direction by comparing the time change of temperature observed by the experiment at room temperature for the C/C composite with the mathematical solution for the heat conduction under one dimension.

Abstract: In this work, a temperature-dependent analytical model was modified to predict the thermal effects of diode laser double–end-pumped cylindrical laser rod under Gaussian pump beam distribution. Heat load and temperature distribution were analyzed using the Kirchhoff integral transform method. Results show that a maximum temperature difference of approximately 69.61 K was obtained on each side face of the laser rod at a maximum power of 40 W (equally divided on each face). The total thermal focal length of approximately 34.64 mm was calculated under the Gaussian pumping profile. The finite element method code incorporated with well-verified software was used to numerically verify the obtained results, where the analytical and numerical results are highly matched. The results reveal that the total thermal focal length produced in a double–end-pumped geometry is two times less than that obtained from a single-end-pumped geometry.

Abstract: Freezing is a physical treatment commonly used in operations such as drying, conservation and lyophilization of foods. In the processing and potato industries, parameters like dimension and initial moisture content of the product has a great effect on the cooling, freezing and post-freezing kinetics. Therefore, this work presents a transient three-dimensional mathematical modeling including phase change to describe the heat transfer during the process, of cooling and freezing parallelepiped foods. The governing equation was solved numerically using the finite-volume technique and a full implicit formulation. As an application, this methodology was used to describe the freezing process of potato (french-fry). Numerical results of the temperature in the center of the product were compared to the experimental data reported in the literature and a good agreement was obtained. Results of the temperature distribution inside the solid and cooling, freezing and post-freezing kinetics are presented and analyzed. It was verified that, the smaller the dimensions and lower the initial moisture content of the product, the solidification of water inside the solid occurs even faster. The largest temperature gradients were identified in the surface, close to the regions of the borders of the solid.

Abstract: This work presents the micro-mechanical models in thermal environment for the vibration behavior of Functionally Graded Materials (FGMs) plate using First-order Shear Deformation Theory (FSDT). In the formulation, the heat transfer effects and the temperature-dependent material properties are considered. Relative estimation of micromechanical behaviors of Mori-Tanaka Method (MTM) is used. And, neutral surface concept is adopted as the reference plane due to the asymmetry in the thickness direction of the model. In the numerical analysis, Finite Element Method is applied for various volume fractions and temperature rising conditions. Also Power-law and Sigmoid FGMs are discussed in thermo-elastic vibration characteristics.

Abstract: We study the influence of chain length of our 1D model of thermal transistor on thermal amplification factor. Here, we varied the length of drain and source segments for different simulation experiment and found that the maximum value of thermal amplification factor influenced with chain length. The thermal amplification factor of the thermal transistor is found to be dependent on gate temperature. We also calculated the switching efficiency and working region of the thermal transistor and better results are obtained in comparison to previous study.

Abstract: Cutting tool temperature which mainly depended on the tool-chip interface temperature has crucial effect on the tool service performance and its life. It is essential to investigate the heat conduction in the cutting tool in order to define the temperature distribution on the cutting tool during machining. Advanced coating materials are adopted to deposit on the carbide substrate to enhance the tools’ cutting performance. Thus, the influence of coating layers on the heat transfer during the cutting process has been an important research topic. Advantage software was employed to simulate the cutting process in this paper. The influences of coating materials on the temperature distribution in the cutting tools were investigated. The study results show that KCU10 cutting tool with TiAlN/TiN coating layers shows good thermal properties than that of KT315 cutting tool with TiN/TiC/TiN coating layers. The cutting temperature along the tool-chip contact length shows increasing trend first with the distance from the tool tip point and then decreasing after the tool-chip separation point. Under the same coating thickness, TiAlN coating material presents better thermal properties than TiN coating material.

Abstract: The paper presents the experimental material on obtaining and researching of three-dimensional composite heat-conducting copper-diamond materials in the system of spark plasma sintering. Earlier [1-5], it was established that in order to achieve the effect of the increased heat conductivity of a composite it is necessary to create the conditions hindering the movement of heat flux on the interface boundary. In this work we have attempted to obtain the material with heat conductivity higher than that of pure copper due to addition of diamond powder and synthesis of the composite in the system of spark plasma sintering. For comparison, we have considered copper and diamond compositions in the ratios of 50/50 and 40/60 correspondingly. The results of the heat conductivity analysis have not exceeded the indices of pure copper; however, according to SEM data, it has been found that at SPS-sintering local domains with enhanced adhesion form on the surfaces of diamonds.

Abstract: The dimensional problem of a formation of the residual stresses in the thin circular elastoplastic plate under the given thermal action was analytically solved. The generalized Prandtl-Reuss thermoelastoplastic model was used. The effect of the non-stationary temperature gradient on the residual stresses field formation was investigated under the condition that the yield stress depends on a temperature. The borders of the irreversible deformation domain and unloading domain were computed. The level of residual stresses was calculated.